摘要:

Charge carrier transport in thermally converted surface layers in semi‐insulating GaAs depends on the generation, diffusion, and occupancy of Ga and As vacancies. The amphoteric nature of C in GaAs can significantly alter the density and the distribution of donors and acceptors in the vicinity of the specimen surface and the surface layer may become eitherptype orntype depending on the thermal treatment conditions.

ISSN:0003-6951    

DOI:10.1063/1.89610

出版商:AIP    

年代:1977

数据来源: AIP

摘要:

Results have been obtained concerning the interrelation of current andC‐Vinstabilities in MOS capacitors subjected to negative gate high‐field pulsing. Rising current transients and negativeC‐Vshifts both show the formation of positive charge in the oxide. However, this charge appears to be situated close to the electrodes rather than in the bulk of the oxide and the temperature dependence of the rate of charge accumulation near the electrodes is different for the aluminum and silicon electrodes. These results indicate that the current instabilities andC‐Vshifts appear to result from independent mechanisms.

ISSN:0003-6951    

DOI:10.1063/1.89611

出版商:AIP    

年代:1977

数据来源: AIP

摘要:

It has been well known that in a long‐channel MOSFET, the experimental value of the threshold voltage obtained by the square‐root extrapolation method in the saturation region agrees well with the theoretical criterion. In a short‐channel MOSFET, the so‐determined threshold voltage depends on the drain voltage because of the drain current dependence on the drain voltageVDS. In this letter, a new method to determine the threshold voltage forVDS=0 V will be discussed.

ISSN:0003-6951    

DOI:10.1063/1.89612

出版商:AIP    

年代:1977

数据来源: AIP

摘要:

Schottky barrier diodes which are specifically designed for use in cryogenically cooled millimeter‐wave mixers have been fabricated from MBE layers grown on heavily doped GaAs substrates. At 15 K the devices show a nearly exponential current‐voltage characteristic and a diode noise temperature which is determined predominantly by the tunneling transport mechanism. A diode noise temperature as low as 55 K was achieved under pumped conditions. This is the lowest diode noise temperature ever obtained in a resistive mixer. A single sideband mixer noise temperature of 315 K was measured at 102 GHz for a cryogenic mixer employing these diodes.

ISSN:0003-6951    

DOI:10.1063/1.89613

出版商:AIP    

年代:1977

数据来源: AIP

摘要:

The traditional hf model of a Schottky diode has been extended to include skin effect, carrier inertia, and displacement current. Above the plasma frequency, results differ considerably from those of the traditional model. The extended model helps understand recently reported detection of 10.6‐&mgr; radiation with Ge diodes doped to only 1016 cm−3.

ISSN:0003-6951    

DOI:10.1063/1.89614

出版商:AIP    

年代:1977

数据来源: AIP

摘要:

A GaAs electro‐optic waveguide switch in which the power isolation in both switch states can be electrically optimized has been demonstrated. The devices exhibit up to 25‐dB power isolation in both states, with total power output constant to within ⩽0.3 dB. The device is formed on one chip and consists of two equal‐length directional‐coupler switches in series separated by a 25‐&mgr;m gap. This structure permits the sign of &Dgr;&bgr;, the electro‐optically induced propagation constant difference between the guides, to be reversed midway along the device length. The loss associated with propagation across the waveguide gap is small (⩽0.2 dB), suggesting that similar gaps could be used to electrically isolate waveguide devices on a common substrate in future GaAs‐based integrated optical circuits.

ISSN:0003-6951    

DOI:10.1063/1.89615

出版商:AIP    

年代:1977

数据来源: AIP

摘要:

We have measured the ac Josephson effect in Nb point contacts at 604 GHz (496 &mgr;m). We find the coupling of the far‐infrared radiation to the point contact to depend in a simple manner on the resistance of the contact. The behavior of the high‐resistance point contacts (50⩽R⩽200 &OHgr;) is very reproducible, allowing a quantitative comparison of the data to the frequency‐dependent Werthamer theory. We also account for the effects of noise and heating and compare these to Tinkham’s heating theory.

ISSN:0003-6951    

DOI:10.1063/1.89616

出版商:AIP    

年代:1977

数据来源: AIP

摘要:

Measurement of stress effects on the critical currentIcof multifilament V3Ga wire are reported, and the cryostat for performing these studies is described. Measurements were taken at 4.2 K in a magnetic field of 9.0 T and for stress values up to 5×108Pa. Noticeable degradation ofIcdid not begin in the wires reported here until stress values of 3.0×108Pa. The first effect of stress was to produce a measurable resistance in the wire belowIc. A discussion of this low‐current onset of resistance is given which suggests that improved stress characteristics in A15 wires may correlate with the reduction or elimination of this resistance.

ISSN:0003-6951    

DOI:10.1063/1.89617

出版商:AIP    

年代:1977

数据来源: AIP

摘要:

Critical currents in a sputtered Chevrel‐phase copper molybdenum sulphide have been measured at 4.2 K as a function of applied magnetic field. Self‐field critical‐current values up to 109A/m2were found, decreasing to 108A/m2at 3 T. Graphs of pinning forces versus field were found to be independent of field direction, and the pinning mechanism is sample independent. Critical‐current densities for sputtered lead molybdenum sulphide are estimated to be ≳108A/m2at 26 T based on a scaling law for pinning.

ISSN:0003-6951    

DOI:10.1063/1.89618

出版商:AIP    

年代:1977

数据来源: AIP

摘要:

The mechanism by which bubble domains collapse and stripe domains chop has been observed in magnetic bubble garnet materials. Single 10‐nsec‐exposure transient pictures taken during the collapse process show that the mechanism of stripe chop and bubble collapse is dominated by the formation of a head‐on wall structure which is nucleated, presumably at one surface, and propagates through the film. In collapsing bubbles, the structure can form before the unstable equilibrium radius is reached. For long stripes in both implanted and as‐grown films, it does not form uniformly along the stripe; thus, sections of stripe will chop to form bubbles. The head‐on wall structure is statically unstable and can only persist for tenths of microseconds.

ISSN:0003-6951    

DOI:10.1063/1.89619

出版商:AIP    

年代:1977

数据来源: AIP